The present invention relates to a seat belt device for protecting a vehicle occupant in a vehicle collision, and more particularly to an air belt device comprising an envelop-like or bag-shaped belt as a part of the seat belt which is inflated with gas from a gas generator.
One air belt device is described in Japanese Patent Unexamined Published Application No. H05-85301. FIG. 9(a) is a perspective view of an air belt device of the application and FIG. 9(b) is a sectional view taken along line B--B of FIG. 9(a).
The air belt device 1 comprises a shoulder belt 2 to be extended at an angle from the right side to the left side of an occupant, a lap belt 3 to be extended from the right side to the left side of the occupant, a buckle device 4 disposed at, for example, a vehicle floor, a tongue 5 to be inserted into and engaged with the buckle device 4 when the occupant wears the belt, and an intermediate guide 6 for guiding the shoulder belt 2.
The shoulder belt 2 comprises a normal belt 2a which is the same as a typical conventional seat belt, and an envelop-like belt 2b connected to an end of the normal belt 2b. The normal belt 2a is guided by and freely slides against the intermediate guide 6. The other end of the normal belt 2a is connected to a seat belt retractor 7 with an emergency locking mechanism (ELR) which is fixed to the vehicle body. The normal belt 2a is provided in such a manner as to be wound into the seat belt retractor 7.
The envelop-like belt 2b is positioned to be in contact with the occupant and is connected to the tongue 5 at an end opposite to the end connected to the normal belt 2a.
The lap belt 3 comprises a normal belt which is the same as a typical seat belt, of which one end is connected to the tongue 5 and the other end is connected to a seat belt retractor 8 with an emergency locking mechanism (ELR) which is fixed to the vehicle body. Connected to the buckle device 4 is a gas generator 9 which acts in case of emergency such as a vehicle collision to generate high-pressure gas.
The tongue 5 and the buckle device 4 are provided with paths for introducing gas from the gas generator 9 to the envelop-like belt 2b.
The envelop-like belt 2b of the shoulder belt 2 comprises a belt body 2c formed in an envelop shape and a cover 2d. The belt body 2c is folded as shown by solid lines in FIG. 9(b) and covered by the cover 2d. The both ends of the cover 2b are then connected by stitching 2e so that the envelop-like belt 2d is normally kept in a band-like shape. The stitching 2e of the cover 2d is easily torn by expansion force of the shoulder belt 2 when the gas generator 9 is actuated so that the envelop-like belt 2b is developed as shown by a two-dot chain line.
Disclosed in Japanese Patent Publication No. S63-39462 is an air belt device in which an inflatable cushion similar to an air belt is attached to a webbing of a seat belt device. The inflatable cushion is made of nylon sheets coated with neoprene rubber. The joint of the nylon sheets is made by suitably stitching in such a manner as to allow gas leak through the joint. The gas leak can reduce the impact applied to a vehicle occupant.
In the above structure for reducing the impact by allowing gas to leak through the joint between the sheets as described in S63-39462, there is a possibility that the gas leaked through the joint directly hits the vehicle occupant. The control of the amount of gas leaked through the joint is quite difficult in practice so that the amount of gas to be leaked can not be controlled to suitably reduce the impact.